Porous compositions utilizing n-car-boxyaminoacid anhydride



Patented Nov. 3, 1953 vLPQROU-S COMPOSITIONS UTILIZING .'N- GAR-.BQXYAMINOACI-D ANH'Y-DRIDE Earl Gluesenkamp, Centerville, Ohio,assignor to Monsanto Chemical Company,"St. Louis, 'Mo.,

a corporation-of Delaware No Drawing. r-iginal application-September$24, 1948,.Serial No. 51,109, noiwtBatent him-2,610,157, dated September.9, 1952. Divided and 'thisapplication January 18, 1952', "SerialNo."267;320

2 Claims. (Cl. ZED-+2.5)

This invention relates to new porous, resinous compositions havingunusual properties as hereinafter described. More particularly, theinvention relates to materials containing uniformly dispersed thereinsmall gas filled cells.

Artificial sponge-like compositions, made from natural gums and resinsand from synthetic resins and rubbers, are well known to the art. Theyare usuallyrnade from thermoplastic poly-- meric compounds bycompounding the polymers with substances which evolve gases when heated,and then heating the blended compositions to form numerous minute gascells. Compositions so obtained have unusually low density and a porouscellular structure.

This application is a divisional application of my copending applicationSerial No. 51,109, filed September 24, 1948, now patent No. 2,610,157.

One purpose of this invention is to provide new improved porous plasticcompositions. A further purpose is to provide new and more effectiveagents for generating the gas within the plastic body. A still furtherpurpose of this invention is to provide a means of incorporating,reinforcing linear polymers within the structure of the porous bodysimultaneously with the production of the gas cells. Other purposes willbe evident in the following description of the invention.

It has been found that when plastic compositions are compounded withN-carboxyaminoacid anhydrides and thenilieated, the resultingcomposition becomes porous by reason of the minute gas cells formed bythe decomposition of the anhydrides. In the blowing operation, thenonvolatile residue of the N-carboxyaminoacid anhydride is polymerizedto form a linear polyamide which serves to reinforce the structure andto modify its physical properties.

The polymerization may be a straight thermal reaction, but in thepresence of traces of initiators, for example, active hydrogencompounds, such as water, alcohols and amines, polymerization of twounits can be effected with the simultaneous regeneration of theinitiator which induces further polymerization in the nature of a chainreaction. In either case, the chemical equation involved is TheN-carboxyaminoacid anhydrides may be those-derived from thea-aminoacids, the structure of which is described in the precedingequation in which the R, R" and R groups may be any alkyl or arylradicals. Alternatively, the aminoacid anhydrides may be derived fromii-amino acids in which case the anhydrides will have the followingstructural formula:

Suitable N-carboxyaminoacid anhydrides are those of N-carboxyleucine,N-carboxyphenylalanine, N-carboxyvaline, N-carboxytyrosine and thecorresponding anhydrides of other aminoacids, for example glycine,alanine, valine, leucine, norleucine, isoleucine, isovaline, as well asaminoacids not occurring naturally which may be synthesized byconventional methods. Other useful aminoacids are those containing aradical substituted on the nitrogen atom.

The clas of compositions which may be processed in accordance with thisinvention are the polymers and copolymers of vinyl chloride. This classof compositions includes polyvinyl chloride and copolymers of upward of70 percent of vinyl chloride, and up to 30 percent of otherpolymerizable monomers, for example, vinyl acetate and other vinylesters of monocarboxylic acids, methyl methacrylate and other alkylesters of methacrylic acid, methyl acrylate and other alkyl esters ofacrylic acid, methyl maleate and other alkyl esters of maleic acid,methyl iumarate and other alkyl esters of fumaric acid, and vinylidinechloride.

In processing the polymers and copolymers of vinyl chloride, it isfrequently desirable to incorporate from five to 40 percent of asuitable plasticizer to render the composition suificiently fiuid atblowing temperatures. Generally, these are more thermoplastic than curedrubber, and, unless heavily plasticized, less resilient.

The new compositions are prepared by milling the plastic with from 2 to30 percent by weight of N-carboxyaminoacid anhydride on a cold mill, orat least at a temperature below the minimum decomposition temperature ofthe N-carboxyaminoacid anhydride, and then confining the sample in asuitable mold in which it is heated to a temperature which induces thepolymerization of the N-carboxyaminoacid anhydride, for example, 125 to200 C. Under such conditions, the N-carboxyaminoacid anhydridepolymerizes with the evolution of carbon dioxide, which forms minute gasbubbles in the polymer and produces the desirable low density and porousstructure. The density of the porous compositions may be changed byvarying the proportion of N-carboxyaminoacid, the most usefulcomposition being prepared with from three to 20 percent.

The invention is defined by the following claims.

I claim:

1. A method of preparing a porous composition, which comprisesintimately dispersing from 3 to 20 percent by weight of anN-carboxyaminoacid anhydride in a vinyl chloride polymer, heating thecomposition to polymerize the Ncarboxyaminoacid anhydride and to formgas cells in the composition.

2. A method of preparing a porou composition which comprises intimatelydispersing from 3 to 20 percent by weight of N-carboxyglycine anhydridein a vinyl chloride polymer and heating the composition to polymerizethe N-carboxyglycine anhydride and form gas cells in the composition.

EARL W. GLUESENKAMP.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,265,559 Watkins Dec. 8, 1941 2,534,283 MacDonald Dec. 19,1950

1. A METHOD OF PREPARING A POROUS COMPOSITION, WHICH COMPRISESINTIMATELY DISPERSING FROM 3 TO 20 PERCENT BY WEIGHT OF ANN-CARBOXYAMINOACID ANHYDRIDE IN A VINYL CHLORIDE POLYMER, HEATING THECOMPOSITION TO POLYMERIZE THE N-CARBOXYAMINOACID ANHYDRIDE AND TO FROMGAS CELLS IN THE COMPOSITION.